Methods using explosive charges and hypergolic liquids to clear minefields are known. One such system uses a rocket to deploy a line charge that, upon detonation, detonates buried mines. The system is mounted on a trailer, and positioned next to a mine field to be cleared. When the system is triggered, a rocket deploys a flexible cord-like charge of explosive, i.e., the line charge, over the minefield. Detonation of the cord on or near the surface of the minefield substantially clears safe lanes for movement. However, a line charge requires placement of the system in close proximity to the minefield, and is not capable of clearing mines submerged underwater or in a surf zone.
Fuel-air explosives have also been used to detonate buried mines. Multiple rocket salvos that disperse clouds of fuel in the form of a vapor or aerosol that mixes with air are fired from a ground based launch platform above a mine field. Detonation of the fuel-air mixture creates a large pressure pulse to initiate mines under the blast. Timing of the fuel-air cloud initiation is complex, as the fuel-air mixture must be within flammability limits. In addition, the method cannot detonate mines submerged underwater or in a surf zone, and again requires the launch system to be in close proximity to mine field.
Mine field clearing systems that require close proximity to the mine field and cannot clear underwater mines are typically only capable of clearing inland mine fields using troops that are already in place on the ground. Therefore, such systems cannot be used to clear surf zones and beach areas to support amphibious landings.
As a result, high explosive munitions have been used to clear mines for amphibious landings. An area known to contain mines is repeatedly bombarded with high explosive weapons in an attempt to damage, detonate, or otherwise displace the buried mines. The method is highly ineffective, requiring multiple salvos. In addition, such a bombardment is typically not capable of clearing mines submerged underwater or in a surf zone. The method may also damage the landing area, rendering the beach unusable for amphibious operations. The use of high explosive weapons can also result in the additional problem of unexploded ordnance (UXO) when one or more of the weapons fail to detonate.
High velocity projectiles, also known as penetrators, filled with an explosive charge or hypergolic liquid, have recently been developed to defeat mines prior to an amphibious landing. The projectiles are reportedly capable of defeating at least a portion of buried and underwater mines deployed in beaches and surf zones. In addition, the penetrators can be deployed from over the horizon with guided or gun launched munitions to clear landing areas prior to troops being put on the ground.
An explosive filled, high velocity projectile or penetrator is intended to penetrate a mine and detonate after a short delay. The shock from the detonating projectile initiates the mine fill, resulting in a high order detonation or structural failure of the mine. This requires precise fusing, as detonation of the penetrator must occur inside the mine to be effective. Reliable target discrimination and timing are a challenge, as the penetrating projectile is typically initiated by impact with the mine case, which may be made of a wide variety of materials, ranging from soft plastic to hard steel. Where the target is relatively thin or lightly cased, and the projectile velocity is high, the projectile may detonate after passing though the target rather than inside. This may damage the mine without detonating or disabling the device. In addition, where the fusing fails to function on impact, or the target is missed, the penetrator may not initiate, creating an unexploded ordnance issue in the target area. A penetrator containing an explosive fill must also contain a safe and arm (S&A) mechanism to allow for safe handling, transport, and storage. Safe and arm mechanisms reduce reliability, reduce the energetic payload volume of a penetrator for a given size and add significant cost to the penetrator.
A projectile filled with hypergolic liquid is intended to penetrate a mine, and fracture the explosive fill. The payload section, containing the hypergolic liquid, ruptures on impact, allowing the liquid to permeate throughout fractured explosive fill of the mine. The hypergolic liquid reacts chemically with the nitro groups of the explosive fill, generating considerable heat and flame, and, preferably, igniting the explosive fill. The extent of the fracturing of the explosive fill of the mine determines the effectiveness of the hypergolic liquid. Without exposure of a sufficient amount of surface area of the explosive fill to the hypergolic liquid, the energetic material in the mine will not ignite readily and sustain combustion.
In addition, the penetrator must reliably rupture on-target when encountering a variety of mine case materials and overburdens. Typical overburdens of many target devices include water, sand, dirt, wood, or sheet metal. These overburdens offer similar resistance as soft plastic target cases. In addition, where the mine is submerged, water may render the hypergolic liquid ineffective by diluting or washing away the hypergolic liquid before reaction with the explosive fill.
There are also many different energetic fills used in mines. A given hypergolic liquid may be quite effective against one type of energetic fill, but totally ineffective against another. Hypergolic liquids are also extremely toxic, and, thus, pose a handling and storage risk should an unintentional leak or rupture of the penetrator occur.
U.S. Pat. No. 6,401,591 reports a device for clearing mines. The device has a housing assembly with a chamber that carries a surface contact chemical reportedly capable of consuming an explosive fill within a mine. A nose assembly, attached to the housing assembly, separates from the housing assembly when the device contacts a solid mass. The nose assembly is reportedly capable of penetrating a mine housing, and contacting the mine explosive fill sufficiently to expose the fill, such that the surface contact chemical can consume the fill. A plurality of the devices reportedly can be used to conduct a mine clearance operation in a surf zone or on a beach.
As discussed above, the extent of the fracturing of the explosive fill of the mine determines the effectiveness of the surface contact chemical. Without exposure of a sufficient amount of surface area of the explosive fill, the energetic material in the mine will not ignite readily and sustain combustion. In addition, the penetrator must reliably rupture on-target when encountering a variety of mine case materials and overburdens, and, where the mine is submerged, water may render the surface contact chemical ineffective by diluting or washing away the chemical before reaction with the explosive fill.
U.S. Pat. No. 6,748,842 reports a kinetic energy driven projectile for defeating unexploded ordnance or buried land mines. The projectile has a small amount of insensitive high explosive material that is cap sensitive in one tip of the projectile, along with an initiation mechanism. Detonation of the high explosive material reportedly more fully fractures the explosive material within a mine, allowing a neutralization agent to completely react with all of the explosive material within the mine, and consume the entire fill. As discussed above, detonation of the explosive in the projectile must occur inside the mine to be effective.
U.S. Pat. No. 6,540,175 reports a system and a method for deflagrating/detonating anti-tank and anti-vehicle land mines, beach zone mines, and surf zone mines located in mine belts or individually using delayed active ignition high temperature incendiary flechettes or darts that are dispersed over a target. Each flechette or dart reportedly has a cavity generating nose geometry, active ignition system employing a firing pin approach, reactive fill, body assembly, and tailfins to allow them to penetrate the soil or water overburden of the mine or the mine directly in surface positioned mines to fracture the mine fill and ignite that fill to cause deflagration or detonation using the high temperature incendiary fill contained in the countermine dart. The delayed ignition system ignites the high temperature incendiary fill of the flechette or dart at impact with the plastic or steel-cased mine. The reaction time from the point at which the flechette or dart hits the mine to the point at which the energy is released is on the order of 50 microseconds. Thus, the reported flechette or dart requires impact with the target for ignition.
U.S. Pat. No. 7,004,073 reports a bellows, spool, and collar system for dispensing projectiles and sub-munitions in a predictable and uniform pattern. The system uses a plurality of spools, packed with projectiles, where the spools are packaged in a missile, bomb, or similar tubular device with an energetic bellows actuator between each spool. The energetic bellows actuator expands rapidly to push a spool of projectiles out of the tubular housing.
U.S. Pat. No. 6,546,838 reports a projectile for the destruction of unexploded ordnance. The projectile is a dart filled with a reactive composition of a metal, an oxidizer, and a binder. The reactive composition is carried by the delivery dart to the mine, and is then initiated.
U.S. Pat. No. 6,691,622 reports a projectile for the destruction of unexploded ordnance containing a reactive composition of a metal and an oxidizer. The reactive composition is only initiated after the projectile impacts the mine.
U.S. Pat. No. 6,354,222 reports a projectile and a method for the destruction of normally explosive targets by deflagration that can be used in existing rapid fire guns without modification. The projectile uses a tracer material, ignited when the gun is fired, to ignite an intermetallic material in the projectile. The intermetallic is ignited after the projectile leaves the gun. The projectile is designed to impact the target and distribute hot fragments throughout the high explosive material of the target, causing deflagration.